This invention relates generally to orthodontic appliances and is particularly concerned with an improvement in attaching a Herbst mechanism to the maxillary arch.
Herbst mechanisms are used in treatment of orthodontic conditions where it is desired to use the natural jaw closure force to move the mandibular arch anteriorly. The usual form of Herbst mechanism comprises a pair of telescopically engaged members, i.e. a tube and a shaft, and usually an appliance contains two such mechanisms, one on each side of the arch. Each mechanism is disposed between the arches, and is attached to the maxillary arch at a more distal location than it is attached to the mandibular arch. In response to jaw closure, the telescopically engaged members of each mechanism assume a force applying position whereby an anteriorly directed force is exerted on the mandibular arch. This force may be developed by an interference between the telescopically engaged members which limits the extent to which the members can telescope and/or it may include a spring mechanism operatively arranged to develop force between the telescopically engaged members.
Various means of attachment of a Herbst mechanism to the respective arches are known. The attachment of a mechanism may be to one or more teeth of an arch. For example attachment to arch wires is a known technique. The arches may or may not be stabilized as a unit depending upon the specific treatment procedure for a particular patient.
The following patents relate to various known appliances:
U.S. Pat. No. 3,158,934 PA1 U.S. Pat. No. 3,654,702 PA1 U.S. Pat. No. 3,690,003 PA1 U.S. Pat. No. 3,798,773 PA1 U.S. Pat. No. 4,424,032 PA1 U.S. Pat. No. 4,462,800 PA1 French Pat. No. 1079955
The present invention is directed to a new and improved means for attaching a Herbst mechanism to the maxillary arch. It comprises a number of important advantages over prior types of attachment.
One important advantage of the invention is that ease of placement and removal of the appliance is enhanced. Much of the tedious work which is often associated with application of an appliance to a patient can be done extra-orally before intra-oral placement. After intra-oral placement, adjustments can be easily performed in a convenient and facile manner to correct midline, etc.
Another particular advantage is that the invention can readily fit all standard head gear tubes without any modification. In the case of an emergency involving breakage or the like, the attachment can be relatively easily replaced.
Since in the preferred embodiment of the invention the adjustment is associated solely with the maxillary arch, the invention is well-suited for use with virtually any type of attachment to the mandibular arch.
A still further attribute to the invention is that it can be used not only as a sole treatment procedure, but in the case of multiple treatment procedures, can also be used in conjunction with other maxillary orthodontic appliances such as full bands, rapid palatal expansion, quad-helix, etc.
While one important advantage of the invention is its convenient adjustability by the treating professional, it has important functional attributes involving the treatment procedure. One of these attributes is that the attachment comprises a certain limited looseness in fit with respect to the maxillary arch which can be beneficial in minimizing the risk of breakage under certain patient-induced situations. In many cases it also allows for the use of a full length Herbst tube. Longer working parts of the Herbst mechanism are advantageous because they are less likely to disengage when the patient opens his or her mouth. The invention also has the advantage that in many patients it will be unnecessary to replace the Herbst tubes since the adjustment in the attachment to the maxillary arch performs a function which can otherwise be accomplished only by increasing the tube length.
Briefly, the attachment means depicted by the preferred embodiment of the invention as illustrated herein comprises a shaft passing through a standard headgear tube on the maxillary arch, typically in the molar region, and with the point of connection of the Herbst mechanism to the shaft being distal of the tube. An adjustable locking device is disposed on the shaft mesial of the tube. When the patient closes his or her mouth, the natural closure force results in corrective force being applied to the mandibular arch through the Herbst mechanism and its attachment. When the appliance is developing the corrective force, the locking device on the shaft abuts the tube, and it can therefore be appreciated that the locking device limits the extent of distal displacement of the point of connection of the Herbst mechanism from the tube. That portion of the shaft between the point of connection to the Herbst mechanism and the locking device has a mesial-distal slip fit through the tube and can rotate to some degree within the tube to provide a certain limited amount of looseness in operation just before the locking device abuts the tube. This looseness can be useful in promoting patient comfort and possibly preventing breakage in some situations.
During the course of treatment procedure, the locking device may be repositioned on the shaft to periodically reduce the amount by which the shaft can project distally from the tube. In other words the point at which the Herbst mechanism connects to the maxillary arch is increasingly moved mesially at periodic adjustment intervals, and this has the effect of increasing the length of the tube of the Herbst mechanism but without any need to actually replace the tube. The end result is that the appliance can be activated or adjusted during treatment to sequentially move the lower arch mesially, without the need for removing the appliance from the patient's mouth. It can be appreciated that this is a significant convenience for both the treating professional and the patient. Because the locking device is disposed mesial of the tube, it is conveniently accessible to the treating professional for adjustment.
The particular locking device is especially compact so that the attachment is quite compatible with a patient despite the fact that it may have to react substantial force when it bears against the headgear tube. The particular construction of the locking device which is used in the preferred embodiment has further advantages which will be detailed later on.
The foregoing features, advantages and benefits of the invention, along with additional ones, will be seen in the ensuing description and claims which should be considered in conjunction with the accompanying drawings. The drawings disclose a preferred embodiment of the invention according to the best mode contemplated at the present time in carrying out the invention.